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Steve Poppe, Horticulture Scientist
Emily Hoover, Dept Head/Professor
Andy Petran and Jack Tillman, Graduate Students
Emily Tepe, Research Associate
Esther Jordan, Communications Specialist
University of Minnesota Day-neutral Low Tunnel
Strawberry Project
Background
• Strawberries are an important part of a healthy diet
• Short MN growing season
• Day-neutral cultivars available to extend strawberry harvest
• Use of organic production methods
• Funding provided by the North American Strawberry Growers Association (NASGA) and the
MN Dept. of Ag, MN Specialty Crop Block Grant
Long Term Impacts:
• Extend the harvest season and increase yields
• Aim to enhance profits
• Increase supply of locally produced organic strawberries
• Fruit available during a non-traditional time
Why Low Tunnels instead of High Tunnels
In high tunnels:
• Space not used efficiently due to strawberry plant stature
• Increased incidence of diseases and insects
• Wind and snow damage
• Temperature gradient high between inside and outside
2015-2016 Project Objectives
• Grow Albion day-neutral strawberry plants on a raised bed in an open field vs. in a low tunnel system
• Develop recommendations for nitrogen requirements
• Evaluate production, fruit quality, pest, weed and disease management throughout the season
• Educate and develop more strawberry growers in the upper Midwest region
2015 Summary: Morris Albion yield and berry weight
Treatment Fertility RateAverage Yield/Plant (lb)
Average Yield/Acre (lb)
Average Berry Weight (g)
Low Tunnel
0x 1 ab 18450 ab 11.4 ab
0.5x 0.75 c 13710 c 9.2 c
1x 0.82 bc 14991 bc 9.8 bc
1.5x 1.12 a 20446 a 11.9 a
1-0x 0.94 abc 17228 abc 10.5 abc
No Low Tunnel
0x 0.95 17278 10.1
0.5x 0.86 15687 10.1
1x 1 18414 10.3
1.5x 0.92 16828 9.7
1-0x 0.9 16467 9.4
2015 Summary: St. Paul Albion yield and berry weight
Treatment Fertility RateAverage Yield/Plant (lb)
Average Yield/Acre (lb)
Average Berry Weight (g)
Low Tunnel
0x 0.78 13263 10.1
0.5x 0.76 13933 10.9
1x 0.71 12991 8.8
1.5x 0.79 14393 10.7
1-0x 0.91 15493 9.6
No Low Tunnel
0x 0.55 b 9933 b 10.3
0.5x 0.79 ab 14330 ab 10.4
1x 0.61 ab 11081 ab 9.7
1.5x 0.61 ab 11164 ab 9.6
1-0x 0.85 a 15493 a 9.8
Harvest
• Strawberry flowers removed 3 times
• Removed strawberry runners 3 times during the growing season
• Typically, harvest begins around the 3rd or 4th week of July
• Picked fruit until mid October
A Noticeably Sweet Berry
• Brix is a measure of total soluble solids
• Albion has relatively high brix compared to other day-neutrals
• Our 2013 June-bearing variety trial had an average brix level of 7.7
• Brix content more influenced by harvest date than fertility of tunnel presence (St Paul)
Brix Content, St Paul 2015
8.20.15
LT
0x 6.45
0.5x 8.01
1x 7.15
1.5x 6.73
1-0x 6.63
PL
0x 6.96
0.5x 7.24
1x 7.31
1.5x 7.01
1-0x 6.45
9.10.15
LT
0x 5.40
0.5x 5.45
1x 5.75
1.5x 5.54
1-0x 5.55
PL
0x 5.11
0.5x 5.83
1x 5.68
1.5x 6.06
1-0x 5.88
10.19.15
LT
0x 10.68
0.5x 11.08
1x 10.51
1.5x 9.52
1-0x 10.33
PL
0x 10.33
0.5x 9.24
1x 10.89
1.5x 9.93
1-0x 10.92
Temperature and Humidity
• Temperature and humidity recorded in the low tunnel and non-low tunnel beds
• Data loggers suspended 12 inches above both beds
Temperature and Humidity
2013 2014 2015
Low tunnel Non-low tunnel
Low tunnel
Non-low tunnel
LowTunnel
Non-lowTunnel
Average temperature
71.3 F 68.2 F 64.6 F 63.6 F 67.3 F 66.2 F
Average relative humidity
82.4% 74.1% 78.2% 70.7% 81.7% 56.1%
Average due point
63.5 57.8 56.4 51.8 60.3 54.9
Variable costs
Total low tunnel
Treatmentper 100'
Fertilizer $70 $11.67
Pesticides $17 $2.78
Plants $125/1000 (w/o
shipping)
approx. 17,500
plants/acre$25.00
Irrigation - drip tape $13/acre $2.22
Mulch - Plastic (white on black) $112.00/9600’ of row $5.00
1.5 mil Clear Film Roll $176.00/1640” $11.00
Galvanized Steel Hoops placed
every 5” (Quantity: 20)$3.98 $79.60
Straw (for walkways) $56.00 $9.33
Hoops for beginning and end of
each row, anchor pipe, steel stakes
to anchor hoops and elastic bungee
53.44
Tractor Fuel (tillage, bed prep,
plastic laying)
approx. 1 gallon/hour
approx. 20 hours
per acre,
$3.50/gallon
$3.50
1 lb. plastic qt. containers
$0.05
approx. 1 lb per
plant & 200 plants
per 100' row
$10.00
Total costs (variable + fixed)$213.54
Expenses (labor not included)
Projected Profit
Projected profit based on 2015 data
Average total yield/plant 0.831 lbs
Estimated marketable yield/plant (15% loss) 0.706 lbs
Average marketable yield/100’ row 141.2 lbs
Average selling price/pound X $5.00
Gross profit/100’ row = $706.00
10 hrs labor to pick 100’ row x $9.50/hr - $95.00
Total costs (variable and fixed, from last slide) - $213.54
Net profit/100’ row = $397.46
1 acre (660’ x 66’) ≈ 72.6 100’ rows*
Net profit/acre $28,855.60
* 6’ row spacing
Low Tunnel Construction and Planting Steps- 2015
Materials needed:
• Bed shaper
• Mulch machine
• 4 foot wide, 1 mil white on black plastic mulch
• Drip tape irrigation
• Dormant day-neutral strawberry plants
Creating a Raised Bed
Creating a Raised Bed
• Once the bed is created, a 4 foot wide 1 mil white on black plastic mulch is placed on top of the bed
• The dry wheel puncher makes small holes in the plastic to act as a guide for proper plant spacing
Creating a Raised Bed
Planting
• Row spacing was 14 inches between rows, and 12 inches between plants in a staggered row
• Use a 1 inch x 12 inch wooden plant stake to transplant
• Place the blunt end of the wood plant stake at the tip of the roots and insert the transplant into the ground
Low Tunnel Support
Use pipe to anchor plastic hoop at the beginning and end of each row
Installing hoops and anchor stakes
Installing Tunnel Plastic
1.5 mil clear film roll
Securing Plastic Hoop with Elastic Bungee
Fertilizer Injector
• At grower sites, fertilizer applied through Ez-Flo injector
• Applied AgGrand 4-3-3 water soluble organic fertilizer through drip tape
Fertilizer Treatments
• Chilean Nitrate, organic
fertilizer, 16-0-0
• Perforated centrifuge tubes
‘planted’ in the soil next to
each plant
• Fertilizer solutions were
mixed for each treatment in
another centrifuge tube
• One ounce of solution is
poured into each perforated
tube beside each plant using
this funnel device
Spotted Wing Drosophila (SWD)
• Very few, if any, SWD were detected in our traps at the Morris or St. Paul sites in 2013, 2014, or 2015.
• Applied Oxidate (OMRI Approved) for control at 1 oz./1 gallon water on a weekly basis at the Morris site
Spotted Wing Drosophila Traps
• Clear plastic quart-size cup, with lid
• Drilled 3/16” holes around the cup • Wire handle inserted into the sides • Yellow sticky traps inside the lid • Trap cups monitored weekly • New bait each week
Recipe for SWD trap bait:• 12 fl oz water• 4 T sugar• 1 T active dry yeast• 1 T apple cider vinegar• 1-2 T whole wheat flour
Tarnished Plant Bug• Damage occurs when the insects use
their sucking mouthparts to “drink” the sugars out of developing fruit
• Results in distorted, cat-faced berries at maturity
• Pressure was noticeably higher in 2015 than in 2013-2014 leading to a reduction in total and marketable yields
• Present in both low tunnel and non-low tunnel treatments, however the damage was more severe in the non-low tunnel in early season at St. Paul
• At both sites a variety of organic insecticides were applied on a weekly basis
• Insecticides used were Mycotrol, Purespray Green, Pyganic and Oxidate
Strawberry Leaf Spot
• Infection is a continuous process with older lesions producing spores to infect young leaves during each season
• Spores are carried to new leaves by rain splash causing the disease cycle to begin again
• More prevalent on the non-low tunnel plant leaves versus the low tunnel
Strawberry Leaf Spot Control
• Most organic fungicides and biocontrol agents are not highly effective against overall disease complex on strawberry
• Products containing sulfur or copper have little or no activity against most leaf spot diseases
• In order to apply sufficient copper to obtain control, the potential for plant injury is probably unacceptable
• Emphasis for controlling these diseases should be placed on selection and use of disease resistant cultivars
New alternative disease control materials for strawberries.
• Messenger
• Oxidate
• Trilogy
• Trichodex
Many of these products have great potential but under moderate to high disease pressure effectiveness is uncertain.
Information taken from Organic Small Fruit Disease Management Guidelines-Ohio State University
Iron Chlorosis Issue
• Chlorosis in day-neutral cultivars due to high soil pH
• Yellow foliage indicates a lack of chlorophyll, the green pigment responsible for photosynthesis (sugar production) in plants
• This photo shows chlorosis on plants that are planted in a soil that measured 7.6 pH
• We have determined that these newer day-neutral cultivars will grow successfully in soils that have a pH of 7.3 or lower
Dubois Retractable Tunnel System Advantages
• No wind damage issues
• Faster/simpler to install as compared to our original system
• Less costly than original system
Concerns
• Slight tearing of hoop plastic
• Our original 4 mil thick plastic provided better heat retention in October
• Sides tend to roll down
What We Learned
• Skillful management required throughout entire growing season
• Fertility: Need 2nd year of data to make conclusions
• Multiple cultivars is better
• Faster installation of Dubois retractable tunnel system
• Insect and disease pressures posed significant challenges in 2015
… this has the potential as a real production system
Special thanks to Nourse Farms for donating strawberry plants for the 2015 trial season
Portola
University of Minnesota West Central Research and Outreach Center
Morris, MN
Steve Poppe
Horticulture Scientist
Andy Petran
Graduate Student
For more information visit our low tunnel blog
http://fruit.cfans.umn.eduAlbion
